While doing multiple courses, honing my practical hacking skills, and reading through dozens of blog posts and cybersecurity updates, I often encountered the information that asymmetric encryption algorithms are more secure than symmetric ones.

Please, have a look at some examples:

Source: https://preyproject.com/blog/types-of-encryption-symmetric-or-asymmetric-rsa-or-aes

Source: https://www.geeksforgeeks.org/computer-networks/difference-between-symmetric-and-asymmetric-key-encryption/

Source: https://stationx.net

Why does it make sense? In case of symmetric algorithms, we use a single shared secret key. In the asymmetric ones, we've got a pair: one private and one public. So clearly, one private + one public seems harder to break than just one shared secret. That was my understanding of the matter before I started my research.

However, some questions remained without answer. Like for example, what if an algorithm is possible to crack without having a key? To find out, I deep-dived into the topic.

ASYMMETRIC ALGORITHMS

Asymmetric algorithms (like RSA) are based on theoretical mathematical problems, such as factoring large numbers. A hacker with enough time and resources could solve these problems faster than they could perform a brute-force attack on symmetric algorithms. That’s why you just need longer keys to achieve the same level of protection and... Everything is sorted, right?

Yes - but only if you don’t care about time and other processing resources.

The problem with asymmetrically encrypted data is that it's heavier and the process is much slower than symmetric encryption. That’s why, for most data types, symmetric encryption is the preferred choice.

SYMMETRIC ALGORITHMS

On the other hand, symmetric encryption (like AES or ChaCha20) doesn’t rely on number-theoretic mathematical problems. Instead, it uses confusion and diffusion - two concepts that scramble the data in a way that makes it practically impossible to undo without the exact key.

To encrypt something, you transform the original data (called plaintext) into ciphertext - a scrambled, unreadable version of the plaintext. Confusion makes the relationship between the key and the ciphertext complex enough to prevent obvious guesses. Diffusion spreads the input data (text, files, network packets, etc.) throughout the ciphertext so that one small change affects everything.

THE DOORS - EXAMPLE

Imagine a situation:

Door A has 128 locks, and each lock is very strong.

Door B has 2048 locks, but they are much easier to pick.

Even though Door B has more locks (bits), Door A could still be harder to break.

BITS AND BOBS - RELATIONS BETWEEN ENCRYPTION TYPES

Now, call me crazy, but wanting to dig deeper I read a big chunk of the NIST Special Publication 800-57 (Recommendation for Key Management) to understand how symmetric and asymmetric encryption relate to each other. Here are my findings:

AES-128 128 bits ≈ 128 bits of security

RSA-2048 2048 bits ≈ 112 bits of security

AES-256 256 bits ≈ 256 bits of security

RSA-4096 4096 bits≈ 150 bits of security

What’s the “bit of security,” someone might ask?

If an algorithm has n bits of security, it means that an attacker would need about 2^n operations to break it (using the best-known attacks, of course). Hence, 128-bit security means that around 2^128 operations would be required - a number that’s impossible for current computers to reach.

On pages 54–55 of the NIST document, you can also find how AES security bits relate to RSA key lengths:

RSA-2048 ≈ AES-112

RSA-3072 ≈ AES-128

RSA-7680 ≈ AES-192

RSA-15360 ≈ AES-256

We can’t realistically use extremely long RSA keys to match the security level of high-bit AES encryption. Currently, to secure the most sensitive documents (e.g., long-term contract signing), we often use RSA-4096, which provides about 150 bits of security strength.

But why not just create and implement a super-long RSA key that covers the safest AES security level?

Because it’s not efficient. RSA is already slow - and it gets exponentially slower as the key size increases. Decryption and digital signing would become dramatically slow.

So in this case, we’re sort of trading unbreakable security for performance.

WHY IS ASYMMETRIC ENCRYPTION COMMONLY CONSIDERED BETTER?

I’ve noticed that when we talk about encryption security, there are two distinct layers to consider.

The first layer is related to the keys. In symmetric encryption, the same key is used for both encryption and decryption. If this key is intercepted, an attacker could decrypt the data without even trying to solve the underlying encryption scheme. Asymmetric encryption, on the other hand, uses a pair of keys - one public, one private - which makes it feel inherently more secure. I’m not here to argue against that.

But then there's the second layer - and it's rarely discussed. This one involves breaking the underlying mathematical problem that each encryption algorithm is based on.

If a hacker could solve that problem, they wouldn’t need any keys at all - not public, not private. They could essentially crack the algorithm itself, generate valid keys, and decrypt all data.

That’s exactly what quantum computers are slowly moving toward. The message conveyed commonly is simple: asymmetric encryption is more secure than symmetric encryption.

Is that true? Sometimes. Is it the whole truth? Definitely not.

If not for my intuition and natural curiosity nudging me deeper, I’d probably believe it too - and just follow the crowd.

KEY-LESS DECRYPTION – EXAMPLES

The next question I asked myself was:

Has it ever actually worked? Have computers managed to crack encryption algorithms and decrypt securely protected information?

The worrying answer is - yes, they have.

For example:

In 2000, RSA-512 was cracked.

In 2009, RSA-768 was cracked too.

Early versions of TLS (Transport Layer Security) were also compromised.

Even ECC (Elliptic Curve Cryptography), considered more secure than RSA though still asymmetric, while not fully broken, has shown vulnerabilities and been weakened.

So that’s some data regarding the asymmetric encryption security.

But what about symmetric encryption?

The answer is simple - two most commonly used symmetric algorithms - AES-128/256 and ChaCha20 - remain unbroken to this day.

…AND NOW WHAT?

Knowing all of that, should we just abandon asymmetric encryption now that anyone with a powerful enough computer might crack it like a peanut shell?

In fact, most systems today combine both encryption types - and this is currently considered best practice, especially while computers still lack the power to break these schemes easily.

Here’s how it usually works:

The browser uses asymmetric encryption (like RSA or ECDH) to authenticate the server. It's also used to securely exchange a randomly generated symmetric key. Symmetric encryption (like AES) is used to encrypt and decrypt the actual data exchanged between client and server.

This combination ensures that data is less vulnerable to key interception or human mistakes. And at the same time, it’s protected by the high performance and strong security of symmetric encryption.

CONCLUSION

In the end, while asymmetric encryption offers practical advantages - like easier key distribution - it isn't inherently much safer than symmetric encryption. Its strength relies heavily on the difficulty of certain mathematical problems, which, although currently hard to solve, aren’t guaranteed to stay that way. Weak implementations, algorithmic flaws, and emerging technologies like quantum computing all pose real risks. Symmetric encryption, on the other hand, though simpler in design, can be extremely secure when used correctly. So rather than assuming asymmetry is always the better option, it’s important to recognize that both approaches have vulnerabilities - and that security depends just as much on proper application as it does on the type of encryption used.

Asymmetric Encryption: Secure Until It's Not